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Typical PC Energy Consumption Reviewed

Dual Core Processors For Low-Power, High-Performance Desktops
By
Component Desktop PC Energy Efficient PC Savings
Processor ~ 30-120 W ~ 10-35 W ~ 60-70%
Platform ~ 15-50 W ~ 10-30 W ~ 20-40%
Graphics ~ 10-120 W ~ 5-25 W ~ 50-80%
Power supply Varying n/a
Other ~ 15-30 W ~ 5-20 W ~ 30-50%
Total power draw* ~ 70-350 W** ~ 35-110 W ~ 50-70%
* Does not include display
** Dual and quad graphics solutions require more energy, as do systems with multiple drives and add-in cards

The table above shows the power draw for typical components, as well as the potential energy savings from using efficient PC parts. You will notice that the savings can vary heavily; this is due to many product options for various components, and their power draw differences:

  • Processor
    Energy consumption increases exponentially with the clock speed. Accordingly, reducing the clock speed will reduce the power draw, especially if energy saving features such as Cool & Quiet (AMD) or SpeedStep (Intel) are used to reduce the operating voltage. In this context, the processor type makes a huge difference as well: a modern 65 nm Pentium D 900 or Pentium 4 6x1 series runs cooler and wastes less energy than the 90 nm Pentium D 800 and Pentium 4 500/600 processors. AMD processors show similar effects from one generation to the next, but the impact is less dramatic due to AMD's more elaborate SOI (silicon on insulator) manufacturing and processor architecture.
  • Platform
    This term refers to the motherboard, including the chipset and on-board components. It comprises functional parts such as audio chips and additional controllers, as well as basic components such as voltage regulators. Intel's current desktop chipsets are not particularly efficient these days, while Athlon 64 core logic benefits from the memory controller being a part of AMD's current processors. However, motherboards that use a mobile chipset rather than a desktop version require considerably less energy.
  • Graphics
    Today's graphics cards are able to squeeze more and more visual effects and even physics calculations out of any graphics processor, but this comes at a tremendous energy price due to the several hundred million transistors used. The basic power draw just for displaying the Windows screen can be 15 to 30 W.
    As the 3D units become active, power consumption increases further; a modern graphics card will convert from 50 to 120 W of electricity into heat. High-end graphics cards even come with a separate power connector to satisfy requirements that exceed the power supply specifications for PCI Express. Of course, dual graphics setups - ATI Crossfire or Nvidia SLI - will almost double the graphics power requirements.
    If you want to save as much energy as possible, there is no alternative to using an integrated graphics solution. Unfortunately, at least today, you must choose between fast 3D graphics and low power operation (see the test results).
  • Power Supply
    Power supplies become less efficient the closer they run to their maximum output, which means that a larger amount of energy will be converted into heat. It is difficult to provide precise numbers, however, because the degree of efficiency varies with the load.
  • Other
    There are other components where power is a concern, such as the hard drive or optical drive, but with these the energy consumption is usually under 10 W. Using 2.5" or even 1.8" hard drives helps to reduce power consumption, but this has a noticeable negative impact on performance. Since the difference in power is not very large, we recommend focusing on other components first.

This article will not deal with all of these components in detail; it mainly addresses the various system and processor options.

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